WO2025032905A1 - Foundation-reinforcing structure for building - Google Patents

Abstract

[Problem] To provide a foundation-reinforcing structure for a building with which it is possible to achieve a short construction period, resource saving, and low cost when a support layer is comparatively shallow or when a base is comparatively good. [Solution] Provided is a foundation-reinforcing structure F for a building, the foundation-reinforcing structure F including a base improvement body 1 having an improved surface-layer base, and foundation concrete 2 poured on the ground improvement body 1. The present invention is used when the position of a support layer of the surface-layer base is 5 m or less from a ground surface, or when the surface-layer base is natural ground, sandy soil, or viscous soil, the N value is 2 or greater, and the lower section of the depth distribution of the N value is not smaller than the higher section thereof. The base improvement body 1 is composed of a higher improvement body 1H and a lower improvement body 1L. The foundation concrete 2 is poured into a recess formed by excavating the base improvement body 1. The higher improvement body 1H is a horizontal plate-form whole-surface improvement body A. The lower improvement body 1L is an independent improvement body B that is positioned below columns 3 of the building above the foundation concrete 2 and protrudes downward from the lower surface of the higher improvement body 1H.

Description

Reinforcement of building foundations

The present invention relates to a foundation reinforcement structure for buildings that is suitable when the supporting layer is relatively shallow or the ground is relatively good.

When the supporting layer is relatively shallow, rappel concrete is commonly used to reinforce the foundations of buildings, replacing the ground below the supporting layer with concrete (see, for example, Patent Document 1).

On the other hand, there is a method of installing a ground improvement body under a slab foundation as a foundation reinforcement when constructing a building on soft ground (see, for example, Patent Document 2). This ground improvement body is made by improving the surface layer of the soft ground, and is composed of a horizontal plate-shaped upper improvement body, a peripheral improvement body that hangs down from the underside of the upper improvement body to form an outer frame, and at least one internal improvement body that hangs down from the underside of the upper improvement body, connects the outer frames, and divides the area inside the peripheral improvement body into multiple areas.

Japanese Patent Application Publication No. 5-214732 Patent No. 3608568

When reinforcing foundations with rapple concrete, it is necessary to set up formwork for pouring the rapple concrete, and in order to set up the formwork, it is necessary to over-dig the excavation hole significantly.

In addition, the local soil in the area where the rapple concrete is poured will need to be disposed of. Furthermore, after the rapple concrete is poured, it will be necessary to backfill the excavated area to the side of the rapple concrete with soil, and the strength of the backfill soil will need to be managed.

In addition, installing the formwork and removing the formwork takes time and effort. Furthermore, because a normal foundation is placed on top of the rappel concrete, it is necessary to install the formwork for the foundation, arrange the reinforcement and remove the formwork, as well as backfill the sides of the foundation with soil, and it is also necessary to manage the strength of the backfill soil.

Foundation reinforcement, which involves installing the ground improvement body under a slab foundation, is suitable for soft ground (for example, ground with a very small N value over a depth of about 20 m).

However, if the target ground is not soft and the supporting layer is relatively shallow, or if the ground is relatively good, the volume of the outer periphery improvement body and the internal improvement body will be larger than necessary in order to form them.

As a result, an increase in the amount of improved soil requires an increase in the amount of cement-based solidification materials and other solidification materials used, and construction time and effort are required. Furthermore, the foundation concrete is a slab foundation in which reinforced concrete is laid over the entire surface of the ground, which makes construction time and effort even more lengthy.

The present invention aims to provide a foundation reinforcement structure for buildings that can be constructed in a short period of time, with reduced resource consumption and at low cost when the supporting layer is relatively shallow or the ground is relatively good.

The gist of the present invention is as follows:

[1]
A foundation reinforcement structure for a building including a ground improvement body obtained by improving the surface ground and foundation concrete poured on the ground improvement body,
This method is used when the position of the supporting layer of the surface ground is 5 m or less from the ground surface, or when the surface ground is a natural ground, which is sandy soil or clayey soil, has an N value of 2 or more, and is a ground in which the N value is not smaller at the bottom than at the top in the depth distribution,
The ground improvement body is composed of an upper improvement body and a lower improvement body,
The foundation concrete is poured into a recess formed by excavating the ground improvement body,
The upper improvement body is a horizontal plate-shaped full improvement body,
The lower improvement body is an independent improvement body located below the column of the building above the foundation concrete and protruding downward from the lower surface of the upper improvement body.
Foundation reinforcement structure for buildings.

[2]
The foundation concrete is an independent foundation;
The foundation reinforcement structure of the building described in [1].

The foundation reinforcement structure of the present invention includes a ground improvement body and foundation concrete poured on the ground improvement body. The upper improvement body of the ground improvement body is a horizontal plate-shaped full-surface improvement body, so that the planar rigidity of the ground surface can be secured, and no underground beams are required. The lower improvement body of the ground improvement body is an independent improvement body and is located below the columns of the building, so that the building load transmitted from the columns to the foundation concrete can be dispersed and transmitted to the on-site ground, and the amount of improved soil is significantly reduced. Therefore, when the supporting layer of the surface ground is relatively shallow (when the position of the supporting layer is 5m or less from the ground surface) or when the surface ground is relatively good (when the surface ground is a natural mountain, sandy soil or clayey soil, has an N value of 2 or more, and is a ground where the N value depth distribution is not smaller at the bottom than at the top), a short construction period, resource saving, and low cost can be achieved.

The foundation concrete is poured into a recess formed by excavating the ground improvement body, so the labor required for formwork construction for pouring the foundation concrete can be reduced. In addition, since there is no need to provide a crushed stone layer that is normally required under the basin concrete, the labor required for crushed stone construction can be reduced. Therefore, in a foundation reinforcement structure for a building used when the supporting layer of the surface ground is relatively shallow or when the surface ground is relatively good, it is possible to achieve a shorter construction period, resource conservation, and low cost.

When the foundation concrete is an independent foundation, compared to a slab foundation or a strip foundation, the structure only has the foundation under the columns, so in foundation reinforcement structures for buildings used when the supporting layer of the surface ground is relatively shallow or when the surface ground is relatively good, it is possible to achieve even shorter construction periods, resource conservation, and lower costs.

1 is a plan view showing an example of a foundation reinforcement structure for a building according to an embodiment of the present invention. 2 is a cross-sectional view taken along the line X1-X1 of FIG. 1. 2 is a cross-sectional view taken along the line X2-X2 of FIG. 1. FIG. 2B is an enlarged view of a main part of FIG. 2A.

The following describes an embodiment of the present invention with reference to the drawings.

[Building foundation reinforcement structure]
An example of a foundation reinforcement structure F for a building according to an embodiment of the present invention is shown in the plan view of Figure 1, Figure 2A, a cross-sectional view taken along the line X1-X1 of Figure 1, Figure 2B, a cross-sectional view taken along the line X2-X2 of Figure 1, and Figure 3, an enlarged view of a key portion of Figure 2A.

The foundation reinforcement structure F of a building includes a ground improvement body 1 that has been made by improving the surface ground G, and foundation concrete 2 that has been poured on top of the ground improvement body 1, and is used when the supporting layer of the surface ground G is relatively shallow (when the position of the supporting layer is 5m or less from the ground surface GL), or when the surface ground G is relatively good (when the surface ground G is natural ground, is sandy soil or clayey soil, has an N value of 2 or more, and is a ground in which the depth distribution of the N value is not smaller at the bottom than at the top).

[Ground improvement body]
The ground improvement body 1 consists of an upper improvement body 1H and a lower improvement body 1L. The upper improvement body 1H is a horizontal plate-shaped full-surface improvement body A. The lower improvement bodies 1L are rectangular column-shaped independent improvement bodies B (nine in this embodiment) located below the steel columns 3 of the building above the foundation concrete 2 and protruding downward from the lower surface D of the upper improvement body 1H.

In this embodiment, as shown in FIG. 1, the planar shape of one upper improvement body 1H is a square, and the planar shapes of the nine lower improvement bodies 1L are also each square.

The height H1 of the upper improvement body 1H and the height H2 of the lower improvement body 1L shown in FIG. 3 are, for example, 300 mm≦H1≦1500 mm and 300 mm≦H2≦1500 mm.

The upper improvement body 1H is a horizontal plate-shaped full improvement body A. This ensures the planar rigidity of the ground surface, eliminating the need for underground beams. The lower improvement body 1L is an independent improvement body B, located below the steel column 3. This allows the building load transmitted from the steel column 3 to the foundation concrete 2 to be dispersed and transmitted to the on-site ground, while significantly reducing the amount of improved soil. Therefore, when the supporting layer of the surface ground G is relatively shallow, or when the surface ground G is relatively good, it is possible to achieve a short construction period, resource conservation, and low cost.

[Concrete foundation]
As shown in Figures 2A and 3, the foundation concrete 2 is poured into a recess C formed by excavating the ground improvement body 1, and is an independent foundation in this embodiment. As shown in Figure 1, the planar shape of each of the nine foundation concretes 2 in this embodiment is a square, and an example of a three-dimensional shape similar to that of the foundation concrete in Japanese Patent No. 6868301 is shown.

The depth of the recess C of the ground improvement body 1 into which the foundation concrete 2 is poured is either within the upper improvement body 1H as shown in Figure 3, is flush with the lower surface D of the upper improvement body 1H, or extends into the lower improvement body 1L.

By pouring the foundation concrete 2 into the recess C formed by excavating the ground improvement body 1, the labor required for constructing the formwork for pouring the foundation concrete 2 can be reduced. In addition, since there is no need to provide a crushed stone layer that is normally required under the basin concrete (see basin concrete 5 in Figure 3), the labor required for crushed stone construction can be reduced. Therefore, in the foundation reinforcement structure F of a building used when the supporting layer of the surface ground G is relatively shallow or when the surface ground G is relatively good, it is possible to further shorten the construction period, conserve resources, and reduce costs.

In addition, because the foundation concrete 2 is an independent foundation, compared to slab foundations or strip foundations, the structure has a foundation only under the steel columns 3, so in the foundation reinforcement structure F of a building used when the supporting layer of the surface ground G is relatively shallow or when the surface ground G is relatively good, it is possible to achieve even shorter construction periods, resource conservation, and lower costs.

The planar shape of the foundation concrete 2 does not have to be a square. That is, the planar shape of the foundation concrete 2 may be, for example, a rectangle, or any polygon with four or more sides. It is a preferred embodiment that the planar shape of the lower improvement body 1L, which is the independent improvement body B, matches the planar shape of the foundation concrete 2, which is the independent foundation. That is, if the planar shape of the foundation concrete 2 is an n-gon, which is a polygon, it is a preferred embodiment that the planar shape of the lower improvement body 1L, which is the independent improvement body B, is also an n-gon.

Furthermore, if the size of the planar shape of the lower improvement body 1L is made larger than the size of the planar shape of the foundation concrete, for example, in Figures 1 and 3, it is set to 0 < E ≦ 1000 mm. Alternatively, the size of the planar shape of the lower improvement body 1L may be set to be smaller than the size of the planar shape of the foundation concrete, for example, -500 mm < E ≦ 0.

[Construction process for building foundation reinforcement structure, etc.]
The foundation reinforcement structure F of a building is constructed, for example, as follows.

<Soil improvement process>
(Drilling process)
The surface ground G below the ground surface GL shown in Figures 2A and 2B and Figure 3 is excavated into the required shape of the upper improvement body 1H, for example, by plowing with a backhoe.

(Primary improvement process)
A cement-based solidification material or other solidification material is spread on the soil in the area where nine rectangular pillar-shaped lower improvement bodies 1L are to be formed. The soil and the solidification material are mixed and stirred using a backhoe or other equipment equipped with a mixing fork as an attachment, and then compacted using heavy machinery and rollers to form the lower improvement bodies 1L.

(Secondary improvement process)
The soil excavated in the digging process is backfilled and spread evenly in the horizontal plate-like upper improvement body 1H using a backhoe or the like. A cement-based solidification material or other solidification material is spread on the backfilled and spread evenly soil. The soil and the solidification material are mixed and stirred using a backhoe or the like equipped with a mixing fork as an attachment, and compacted with heavy machinery and rollers to form the upper improvement body 1H.

<Foundation excavation process>
For the ground improvement body 1 constructed in the ground improvement process, the upper part of the ground improvement body 1 located below the above-ground part of the steel column 3 is excavated to a predetermined depth using a backhoe or the like to form a three-dimensional shape of the foundation concrete 2, thereby forming a recess C.

<Foundation pouring process>
The basing concrete 5 shown in Fig. 3 is poured. The column base anchor bolts for fixing the steel column 3 are fixed to the basing concrete 5, the foundation reinforcement is arranged, and the foundation concrete 2 is poured. The steel column 3 is installed, and the floor concrete 4 is poured.

The above steps complete the construction of the building's foundation reinforcement structure F, etc.

　According to the foundation reinforcement structure of a building according to an embodiment of the present invention, the construction period is about 1/3 compared to, for example, the case of using rapple concrete to reinforce the foundation as in Patent Document 1. Also, according to the foundation reinforcement structure of a building according to an embodiment of the present invention, the amount of improved soil in the primary improvement process is about 1/4 compared to, for example, the case of installing a ground improvement body under a slab foundation as in Patent Document 2, where the ground improvement body is formed by a horizontal plate-shaped upper improvement body, a peripheral improvement body that hangs down from the underside of the upper improvement body to form an outer frame, and an internal improvement body that hangs down from the underside of the upper improvement body, connects the outer frames, and divides the area inside the peripheral improvement body into multiple areas.

The above description of the embodiments is merely illustrative and is not intended to be limiting. Various improvements and modifications may be made without departing from the scope of the present invention.

1 Ground improvement body 1H Upper improvement body 1L Lower improvement body 2 Foundation concrete 3 Steel column 4 Concrete floor 5 Disposal concrete A Full surface improvement body B Independent improvement body C Recess D Underside E Difference between the size of the planar shape of the lower improvement body and the size of the planar shape of the foundation concrete F Foundation reinforcement structure of the building G Surface ground GL Ground surface H1 Height of the upper improvement body H2 Height of the lower improvement body

Claims (2)

A foundation reinforcement structure for a building including a ground improvement body obtained by improving the surface ground and foundation concrete poured on the ground improvement body,
This method is used when the position of the supporting layer of the surface ground is 5 m or less from the ground surface, or when the surface ground is a natural ground, which is sandy soil or clayey soil, has an N value of 2 or more, and is a ground in which the N value is not smaller at the bottom than at the top in the depth distribution,
The ground improvement body is composed of an upper improvement body and a lower improvement body,
The foundation concrete is poured into a recess formed by excavating the ground improvement body,
The upper improvement body is a horizontal plate-shaped full improvement body,
The lower improvement body is an independent improvement body located below the column of the building above the foundation concrete and protruding downward from the lower surface of the upper improvement body.
Foundation reinforcement structure for buildings. The foundation concrete is an independent foundation;
The foundation reinforcement structure for a building according to claim 1.

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